Forty years ago, dairy farmer John Kenyon was approached by a rabbi who was looking to modernise kosher milk production. "I told the rabbi we'd give kosher a go," Mr Kenyon recalls.
Now the John Kenyon & Son dairy produces over 3,000 litres of Mehadrin [strictly kosher] milk a day under the Manchester Beth Din aegis at his 100-acre farm near Bury in Greater Manchester.
Mr Kenyon, 81, has become well accustomed to the rigours of kosher milk production. But when the business first became kosher under the guidance of halachic expert Dayan Yitzchak Weiss, it took some getting used to. "It seemed odd to us at first to have a rabbi supervising us when our hygiene was of the strictest standards. But we've learned what kosher is, and I've brought my sons up with it" says Mr Kenyon, a fourth-generation dairy farmer whose family roots are in Blackburn.
The farm is now run by his 47-year-old son Stuart and three grandsons, who say kosher is second nature to them. "Our kosher skimming machine processes 1,360 litres an hour," Stuart Kenyon explains. "We have a totally separate processing plant and storage for our kosher production which is why we are considered super-kosher. We have a Beth Din supervisor on site and we can't milk without one here."
Historically, milk was supervised primarily to ensure farmers did not adulterate it with that of non-kosher animals. Stuart Kenyon says that nowadays, the Food Standards Agency requires full traceability for UK milk production and regularly tests for any additives, including water.
The robust regulation of milk production is the reason that some halachic authorities deem unsupervised milk to be kosher. But there can be problems. The dairy's Manchester Beth Din kosher supervisor Mosche Neufeld - wearing kippah, wellies and jeans - says there are additional issues he learned about while supervising Swiss chocolate and cheese production in his native country.
"If a dairy produces cheese, yoghurts and other products using non-kosher additives, flavours and colours, they can find their way into kosher milk."
Food for the farm's 400 cows is dispensed in individual computer-controlled troughs to give each micro-chipped animal the perfect feed to obtain the highest milk yield. The system logs a cow's age, daily milk production, weight and even hormonal cycle and awards the cow with up to 3kg of pelleted feed in a kind of Weight Watchers points scheme.
Stuart Kenyon reports that kosher production has helped the farm survive the supermarket milk price wars which has damaged the general side of his business. Kosher milk has other advantages, he maintains. "When you buy from a supermarket, the milk is taken from different farms, mixed together and transported in one 28,000 litre tanker lorry.
"It's a bit like the difference between a blended whisky and a single malt. With local kosher production you get a fuller flavour and it keeps for up to 10 days because the milk reaches customers more quickly. As modern customers, we should all demand the same standard we get with kosher food. With kosher you know exactly where your product came from. Even with FSA rules, if there is contamination in non-kosher milk it can take much longer to find the problem because the milk is being being mixed from all over the place."